Why don't your suppliers make the diaphragm out of a material that withstands ethanol, for the YF? E-10 is not going away soon.
Also, what carb would you recommend that would have good MTBF for this engine.
OH, if it were that easy!!!!!
The problem is three-fold:
First, according to our all-knowing government, neopreme is approved for use with ethanol. Thus, the suppliers that make the diaphragms ARE using an approved substance, even though it doesn't work well.
Second, the accelerator pump diaphragm is part of the metering system. It is designed to flex a given amount with a given imput. Change the amount of flex/input, and the height of the metering rod in the jet would change, thus changing the dynamic calibration of the carburetor.
Third, I have checked with a friend that manufactures kits for fuel pumps. The material he is using is buna N rubber with embedded fiberglass particles for strength. Just assuming that the flex rate for the buna N is identical to neopreme (it isn't); buna N/fiberglass does not exist in the proper thickness for the YF diaphragm. And there is insufficient quantity of carburetors left to justify the minimum order to have buna N produced in the proper thickness.
As to what carburetor I would recommend?
Well, the YF is still a great carb, with the caviat of the periodic replacement of the pump diaphragm. And the YF is reasonably priced.
Both Stromberg and Zenith offered excellent carbs with ethanol friendly accelerator pumps, but at a higher initial cost.
Carter also offered a WE with a normal leather accelerator pump (730s was released for the Chevrolet 216, it would probably work well with the 235 on a 216 intake manifold). I have never researched this to check the calibrations. And remember, Chevrolet used the 216 W-1 on 235 engines in the 1940's.
Jon.
